The present invention relates to a hose suitable for conveying refrigerants such as fluorinated hydrocarbons such as Freon.TM. in a liquid or gas phase, liquefied gases such as LPG, gases such as CO.sub.2, O.sub.2 or N.sub.2, or volatile liquids such as gasoline or gasahol.
Refrigerant gas conveying hoses are employed, for instance, in automotive air conditioning systems. A rubber hose having an inner layer of rubber has been employed for such a gas conveying hose. This type of rubber hose is, however, disadvantageous in that refrigerant gas can pass relatively easily through the rubber hose, the material of the rubber hose may be harmed by the substance being conveyed, and the hose is relatively heavy. Therefore, a refrigerant gas conveying hose having an inner layer made of plastic instead of rubber has been proposed and used commercially. However, if the inner layer is made of polyvinylidene chloride or a polyamide copolymer such as Nylon-6, 10 or Nylon-6, 12, which is a plastic material excellent for preventing the permeation of gas, then the flexibility and heat resistance of the hose are decreased. Nylons are melt processible thermoplastics whose chain structure features repeating amide groups. Such are disclosed for example in "Plastics Progress 1955," pp. 129 et seq., edited by Phillip Morgan M. A., Iliffe & Sons, Ltd.
This difficulty may be overcome by using a polyamide copolymer such as Nylon-11 or Nylon-12 . However, in this case, the impermeability factor of the hose will be somewhat reduced. In addition, in the case where the inner layer is made of Nylon-6, 10, moisture in the air may enter the hose during the refrigeration operation which may adversely affect the related operating components. In other words, an inner layer made of Nylon such as Nylon-6 or Nylon-6, 10 of high crystallizability is high in refrigerant gas permeability but low in moisture permeability while an inner layer made of Nylon-11 or Nylon-12 is low in moisture permeability but high in refrigerant gas permeability.
Yet further, it is known in the art that an inner layer made of acrylonitrile rubber (NBR), which has been extensively employed, is low in moisture permeability but high in refrigerant gas permeability.
As can be seen, a conventional hose cannot simultaneously satisfy the desired characteristics as to the moisture permeability and refrigerant gas permeability.